new measurement of time dilation in distant supernovae.

(To the moderators, I had problems replying to original post and hence
am starting a new thread)
Helbig---remove CLOTHES to reply) wrote:
In article , Jonathan

Thornburg writes:
apparent aging rate consistent with the 1/(1+z) factor (where z
is the redshift) expected in a homogeneous, isotropic, expanding
universe. These measurements thus confirm the expansion hypothesis,

I'd just like to point out that the 1/(1+z) factor would also be
expected at least in some inhomogeneous anisotropic universes. In a
universe like ours, which is almost homogeneous and isotropic, the
expectation is certainly very close to 1/(1+z), certainly any
discrepancy would be much less than the observational error. In other
words, an observation of this factor is a robust result indicating that
it arises from the expansion.

This factor and the redshift are really the same thing. One can think
of the frequency of electromagnetic radiation as a standard clock. Thus
the original wavelength is 1/(1+z) as long as the observed wavelength by
the same argument which applies to the supernovae. This is just the
normal redshift.

The interesting thing is that alternative theories which have some other
mechanism for the normal redshift ("tired light" etc) usually don't
predict time dilation in other clocks like a supernova light curve,
whereas in the expanding-universe paradigm, one implies the other since
they are really the same effect.

It is also good to keep in mind that 1/(1+z) tells us the ratio of the
size of the universe at the time the light was emitted to the size of
the universe when the light was detected and the redshift measured.
A clarification. Shouldn't the cosmological time dilation scale as
(1+z)
instead of 1/(1+z)? At least that's how I interpret the curve in :
http://www.astro.ucla.edu/~wright/tiredlit.htm
Larger the redshift, larger the time-dilation or width/length of the
curve. Or am
I misinterpreting this plot?
Or is this new measurement not a direct measurement of width of curve
and something else?
Thanks

In article , Melroy
writes:

This factor and the redshift are really the same thing. One can think
of the frequency of electromagnetic radiation as a standard clock. Thus
the original wavelength is 1/(1+z) as long as the observed wavelength by
the same argument which applies to the supernovae. This is just the
normal redshift.

It is also good to keep in mind that 1/(1+z) tells us the ratio of the
size of the universe at the time the light was emitted to the size of
the universe when the light was detected and the redshift measured.

From the two paragraphs above, it is clear that 1/(1+z) is "then/now".

A clarification. Shouldn't the cosmological time dilation scale as
(1+z)
instead of 1/(1+z)? At least that's how I interpret the curve in :
http://www.astro.ucla.edu/~wright/tiredlit.htm
Larger the redshift, larger the time-dilation or width/length of the
curve.

Right. 1/(1+z) is the ratio of the real timescale to the observed
timescale. It just depends on what you take as reference quantity.